Over the past decade, we have learned how our brains are hardwired for emotional contagion. Emotions spread via a wireless network of mirror neurons, which are tiny parts of the brain that allow us to empathize with others and understand what they’re feeling. When you see someone yawn, mirror neurons can activate, making you yawn, in turn. Your brain picks up the fatigue response of someone sitting on the other side of the room. But it’s not just smiles and yawns that spread. We can pick up negativity, stress, and uncertainty like secondhand smoke. Researchers Howard Friedman and Ronald Riggio from the University of California, Riverside found that if someone in your visual field is anxious and highly expressive — either verbally or non-verbally — there’s a high likelihood you’ll experience those emotions as well, negatively impacting your brain’s performance.

Observing someone who is stressed — especially a coworker or family member — can have an immediate effect upon our own nervous systems. A separate group of researchers found that 26% of people showed elevated levels of cortisol just by observing someone who was stressed. Secondhand stress is much more contagious from a romantic partner (40%) than a stranger, but when observers watched a stressful event on video with strangers, 24% still showed a stress response. (This makes us question whether we, as happiness researchers, should watch Breaking Bad before going to sleep.)

When your taxi driver honks angrily, you can carry his anxiety all the way to work. When a boss hurriedly stalks into a room, you can pick up her stress as you try to present your ideas. Even bankers on trading floors separated by glass walls can pick up the panic of a person across the room working in a separate market just by seeing their nonverbals.

According to Heidi Hanna, a fellow at the American Institute of Stress and author of Stressaholic, secondhand stress is a result of our hardwired ability to perceive potential threats in our environment. She writes, “Most people have experienced spending time with someone who triggers a stress response just by walking in the door. This can be a conditioned response from previous interactions, but may also be an energetic communication delivered by very gentle shifts in bio-mechanical rhythms such as heart rate or breath rate.” The cues that cause secondhand stress can be very subtle changes in the people around us at work, yet they can have huge impacts.

In fact, you don’t have to see or hear someone to pick up their stress; you can also smell them. New research shows that stress causes people to sweat special stress hormones, which are picked up by the olfactory senses of others. Your brain can even detect whether the “alarm pheromones” were released due to low stress or high stress. Negativity and stress can literally waft into your cubicle.

As the research has become more sophisticated, we see that the negativity we “catch” from others can also impact every single business and educational outcome we can track, and most recently has been shown to impact us down to a cellular level, shortening our lifespan. According to Before Happiness, companies like the Ritz Carlton and Oschner Health Systems, aware of the impacts of secondhand stress, have started instituting “no venting” zones for their employees when around customers or patients. A patient seeing a nurse seething with stress or complaint could catch the contagion as they evaluate the care they receive — not to mention the fact that positive mindset is continually associated with positive health outcomes, as outlined by Tom Rath in Wellbeing.

In our highly connected working world, we are hyper-exposed to other people. This means negative emotions and stress become even more contagious as we have high exposure to negative comments on news articles and social media; stressed body language of financial news shows; stressed out people on our subways and planes; and open office plans where you can see everyone’s nonverbals. In such a highly connected world, we need to find ways to improve our emotional immune system, otherwise we risk the negative effects of second handstress. Here’s how:

Change your response: In research we did at investment banking company UBS with Dr. Alia Crum from Stanford’s Mind & Body Lab and Peter Salovey, founder of the Yale Center for Emotional Intelligence, we found that if you create a positive mindset about stress and stop fighting it, you experience a 23% drop in the negative effects of stress. When we see stress as a threat, our bodies and minds miss out on the enhancing effects of stress. (Even at high levels, stress can create greater mental toughness, deeper relationships, heightened awareness, new perspectives, a sense of mastery, a greater appreciation for life, a heightened sense of meaning, and strengthened priorities.) Instead of fighting and being frustrated at negative people around you, take it as an opportunity to feel compassion or a challenge to help that person become more positive. Our HBR article “Making Stress Work for You” includes more ideas on how to change your stress mindset to a more positive one.

Create positive antibodies: We need behaviors that can neutralize the negative effects of a stressed person. Instead of returning a harried coworkers’ stressed nonverbals with an equally stressed grimace of your own, return it with a smile or a nod of understanding. Suddenly you have the power. As suggested in the new book Broadcasting Happiness, you can create a “power lead” to short-circuit a negative encounter. The first comment in a conversation often predicts the outcome. Try to start your phone calls not with “I’m swamped” or “I’m so busy.” Instead, start with a breath and calmly say: “It’s great to talk to you.”

Build natural immunity: One of the greatest buffers against picking up others’ stress is stable and strong self-esteem. The higher your self-esteem, the more likely you will feel that you can deal with whatever situation you face. If you are finding yourself being impacted by others’ moods, stop and remind yourself how things are going well and that you can handle anything that comes your way. Exercise is one of the best ways to build self-esteem, because your brain records a victory every time you exercise, via endorphins.

Inoculate yourself: Inoculate yourself before going into work or stressful environments. For example, before we start our morning, the very first thing we do is think of three things we are grateful for that day. In this TED talk, you will learn the five positive psychology habits that help inoculate your brain against the negative mindsets of others: 1)writing a 2-minute email praising someone you know; 2) writing down three things for which you’re grateful; 3) journaling about a positive experience for two minutes; 4) doing cardio exercise for 30 minutes; or 5) meditating for just two minutes.

Nowadays, we may know to avoid smoking lounges and we wash our hands after being in busy airports, but in the future, we may realize the key to health and happiness is improving our emotional immune system to protect ourselves from others’ stress. And of course, it’s not just other people’s stress that matters — our own mindset affects the happiness of those around us. A positive mindset can improve our own lives, and the lives of everyone around us.